Treatment of HIV infection with a combination of antiretroviral drugs (HAART) has proven to be highly effective in the clinical management of HIV infection. Unfortunately, HAART does not eradicate HIV because it appears to have little effect on the viral reservoir. Recent strategies to improve treatment of HIV-1 infection have focused on immunotherapeutic intervention. However, a vaccine regimen that induces long-term control of virus after removal of HAART requires targeting the vaccine to the source of virus production. We hypothesize that the major reservoir of virus production resides in mucosal tissues. Therefore, a vaccine that induces potent T cell responses in the mucosa is required to provide persistent control/clearance of virus after suspension of HAART. We will test this hypothesis in the SIV:macaque model using a novel epitope-directed DNA vaccine combined with an exciting new genetic adjuvant encoding the heat-labile E. Coli enterotoxin LT that targets mucosal tissues. The vaccine encodes 7 immunodominant SIV-specific CTL and 3 T helper epitopes linked to a highly immunogenic hepatitis core antigen (HBc) carrier gene. The inclusion of multiple, conserved epitopes, together with an adjuvant that induces mucosal responses, should enable control of diverse viral isolates persisting in reservoirs during HAART. In Aim 1 we will test the HBc-epitope DNA vaccine + LT as an adjunct to HAART for therapy of chronic SIV infection. Aim 2 will be directed to characterizing the immune responses induced by therapeutic DNA immunization, both in the periphery and directly in the mucosal tissues. The viral reservoir for persistent viral replication will be identified in Aim 3. SIV sequences expressed in CD4+ and CD14+ cells from mesenteric and peripheral lymph nodes, lung lavage, jejunal lamina propria and in PBMC will be both qualitatively and quantitatively compared during therapy and during rebound after drug is discontinued. Animals will be sacrificed at one year of follow-up so that liver, spleen, bone marrow, and the central nervous system can be similarly analyzed so that the cellular and tissue-specific reservoirs of virus production can be identified. Together, these studies will both define the nature of viral persistence during chronic infection and identify an effective method of treatment.